THOSE IN THE gambling business know how to stack a deck. They also know how to influence politicians with large campaign contributions. So it should come as no surprise that Democrats are playing games with their appointments to a federal commission on legalized gambling. Both President Clinton and House Minority Leader Richard Gephardt seem poised to place pro-gambling people on the panel.

And why not? The gambling industry contributed $4.4 million to federal election campaigns last year. Indian tribes that run casinos pumped some $1.2 million to Democrats. No wonder reports are circulating that the president intends to name a representative of Indian gaming, a gambling official from Atlantic City and the head of the Nevada Gaming Control Board. And Mr. Gephardt's choice? Apparently it will be a Las Vegas union leader sympathetic to gambling.

So much for the fairness of this commission. House Speaker Newt Gingrich had already poisoned the well by appointing the CEO of a giant casino to the panel; the speaker and Senate Majority Leader Trent Lott had also picked a number of Christian fundamentalists solidly opposed to gambling. Few members approach the topic objectively and without bias.

That is unfortunate. The notion of a two-year national study of gambling's impact is a worthy one. Yet Rep. Frank R. Wolf, R-Va., has encountered one barrier after another. Gambling interests spent more than $400,000 to delay or kill the resolution setting up this panel. Now they are intent on making sure the commission sees things the industry's way.

This country's explosion of gambling in the past decade deserves careful scrutiny. How deeply is organized crime involved? Does heightened gambling produce high social costs? What are the positive and negative implications?

We can't count on the national commission answering those questions unless the president, the speaker and Mr. Gephardt re-think their positions and choose credible, impartial individuals for the gambling panel.